Circuit-breaker for three-wire systems



Patented Sept. 20, I898.

No; 6l0,903.

E. ILHEWLETTy CIRCUIT BREAKER FUR THREE WIRE SYSTEMS.

(Applicntion filed Sept. 7, 1897) (No Model.)

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UNITED STATES PATENT OEEIcE.

ED\VARD M. IIEVLET", OF SOIIENEOTADY, NE'W YORK, ASSIGNOR TO THE GENERAL ELECTRIC COMPANY, OF NEIV YORK.

CIRCUIT-BREAKER FOR THREE-WIRE SYSTEMS.

SPECIFIoATION forming part of Letters Patent No. 610,903, dated September 20, 1898.

Application filed September 7, 1897. Serial No. 650,759. (No model.)

To 0.1] whom if; may concern.-

Be it known that I, EDWARD M. HEWLETT, a citizen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Circuit-Breakers for Threeire Systems, (Case No. 621,) of which the following is a specification.

My present invention relates to an adaptaro tion of circuit-breakin g apparatus to the wellknown three-wire system by which a ground on one side or the other will operate the main circuit-breaker at the station and prevent burning out the lamps on the grounded side. I 5 In many three-wire installations the neutral is grounded, and with this arrangement only one circuit-breaker is as a rule employed in the station. If, therefore, a ground occurs on either side of the system, the lamps or equivalent translating devices will be burned out by excess of current. To obviate this, I have devised my present invention, which consists, in addition to the ordinary circuitbreaker of the station, of a device like a relay-m agnet, having differential coils included in the two sides of the three-wire system and designed, by the attraction of its armature, to close a circuit across the outside mains, including an auxiliary coil upon the circuitbreaker, which will trip its latch and so open the circuit.

The accompanying drawings show my invention, Figure 1 being a diagram of the circuits; Fig. 2, a mechanical view with the circuits shown in dotted lines, and Fig. 3 aside elevation of the two coils upon the circuitbreaker.

I will first describe the mechanical embodiment of the invention and therefore refer first to Fig. 2. In this figure the circuit-breaker O B is one of the well-known types, embracing a bridging contact M, connecting the two terminals N N. This is the main circuit. A shunt to these terminals is indicated in dotted lines in the upper part of the figure. This shunt is provided with circuit-breaking contacts and the usual arc-disrupting means. A toggle-lever P is provided for closing the circuit, and a detent 0 engages with the pawl or trip 0, connected to the armature K, operated by the coils D D in a way presently to be pointed out. The spring P serves to open the circuit when the pawl orlatch O is tripped.

On the left in Fig. 2 is shown the relay de vice, comprising coils d d, wound diiferentially, acting to pull down the armature E, with which is connected a bridging-terminal E, held away from the terminals H II by the spring F and which when drawn down by the armature completes a circuit through the coil D upon the circuit-breaker.

In Fig. 3 I show the arrangement of the coils, the coil D being the ordinary series coil designed to operate on overload, and the coil D a shunt-coil in circuit with the relay device for operating the circuit-breaker under the peculiar conditions set out in the statement of invention.

The circuits of the device are illustrated in Fig. 1, where the same reference-letters refer to the same parts as in the mechanical embodiment. In Fig. 1, A is the generator, and B O are compensating dynamos for dividing the voltage of the main generator in the way adapted to the three-wire system. Of course the generator might be omitted and the dynamos B 0 represent a suitable divided source of electromotive force without affecting the essence of my invention, this modification being one readily understood by engineers. 8o \Vith either form of the invention Ct Z) c are the mainspositive, negative, and neutral, the neutral main grounded at G. Leads from these mains are shown at a Z) 0, between which are coupled the differential windings d d of the relay device. D D are the series and shunt coils upon the circuit-breaker O B. The differential coils d d are substantially equal in effect, so that the relay is normally not operated by them, the bridging contact 0 E being held out of contact with the terminals H.

The operation of the apparatus is as follows: The main 1) being grounded and the distribution of current proceeding in the usual way, if 5 a ground occurs-on the main 0, for instancethere will be no difference'of potential across the terminals of the coil (1 connected between these mains. If the grounds were some distance apart, there might be a slight diiference of potential, but practically no current would flow in this coil. The coil d therefore would energize the core of the relay device, pulling down the armature and contact E, closing the circuit across the terminals H. Current would then flow by the lead a through these terminals around the shunt-coil D of the circuit-breaker to the grounded main 0, and the coil would then open the circuit-breaker. A similar action would take place should the main a become grounded.

While the general arrangement of the circuit-breaker shown in this application is not of my invention, I consider it to be new with me to applyto a circuit-breaker a main coil and a shunt-coil operated by different circuits to open the main circuit of the station or of any particular dynamo under different conditions. It will readily be perceived that this broader aspect of my invention is capable of many useful applications, all of which could not be easily outlined in a single specification. It would be possible, as one example, to close the circuit of the coil D by hand from different parts of the station, so that in the event of any accident the main circuit could be at once opened.

What I claim as new, and desire to secure by Letters Patent of the United States, is

1. A circuit-breaking device fora three-wire system, comprising a main switch designed to act upon the circuit of a given dynamo, and a relay device connected across and to each of the outside mains of the three-wire system and in circuit with a coil upon the main switch, the relay device provided with contacts closing the circuit of the coil on the main switch on excess of load in either side of the threewire system.

2. A circuit-breaking apparatus for use in a three-wire system, comprisinga main switch having a plurality of coils, and a relay having differentially-wound coils connected in the two sides of the three-wire system, with a circuit controlled by the relay including one of the coils upon the circuit-breaker.

3. In combination with an actuating-coil upon a circuit-breaker in the main circuit of the station, a relay-magnet havingdifferentially-wound coils connected respectively in the two sides of a three-wire system, and 'a circuit across the outside mains of the three- Wire system including a shunt-coil upon the circuit-breaker and controlled by the relaymagnet.

4. A circuit-breaker comprising a series coil opening the switch upon a definite overload, another normally idle coil also arranged to open the circuit when energized, a circuit including the second coil with a source of current, and a relay device for opening and closing the exterior circuit.

5. The combination, with a series or overload coil and the trip of a c'frcuit-breaker, of an additional or auxiliary coil also acting to open the circuit, and included in another circuit controlled by a relay device.

6. The combination with a series coil carryin g the main current and the trip of a circuitbreaker, of a shunt-coil acting to open the circuit and controlled by exterior contacts.

7. The combination with a series or overload coil and the trip of a circuit-breaker, of an additional coil acting to open the circuit and controlled by an exterior circuit.

In witness whereof I have hereunto set my hand this 3d day of September, 1897.

EDWVARD M. HEWLETT.

Witnesses:

A. F. MACDONALD, A. II. ABELL. 

